What Are the Functions of a HVAC Compressor Fan?

by Susan King; Updated September 26, 2017
What Are the Functions of a HVAC Compressor Fan?

Your air-conditioning system is something you don't think much about until it doesn't work. Then it becomes one of the most important systems in your house. Knowing the basic components of your system will help you diagnose problems and reduce the amount of time a repairman might have to spend at your house, therefore reducing cost and ensuring that the proper parts are on the truck when he arrives. A compressor fan is a complicated part of your HVAC system and has several interconnected pieces needed for it to run smoothly.


The outdoor section of an air-conditioning system is called a condenser. The three main components of the condenser are the compressor, the condenser coil and the compressor, or condenser fan. The function of the condenser fan is to cool the highly-pressurized, hot refrigerant gas to the point where it will condense inside the condenser coil to a sub-cooled liquid. The liquid refrigerant then moves through the smaller tube of the refrigerant line set to the indoor section of the air conditioning system, where it is sprayed through a metering device into the evaporator coil. The refrigerant then returns as a cool gas through the larger refrigerant tube to the compressor where the cycle begins again until the thermostat is satisfied and the system shuts off.

Fan malfunction

If the fan on the condenser fails to operate for any reason the pressures and the heat in the condenser coil will exceed the operating range in less than a minute. The condenser can have up to three safety devices to protect the compressor when the pressures move outside the normal operation range. In an emergency situation a water sprinkler directed at the widest portion of the condenser coil can sometimes do the job of condensing the hot vapor refrigerant until you can get replacement parts or the repairman arrives.

The run capacitor

The run capacitor

Before the proper air-conditioning process can begin again the fan needs to be in good working order. In most cases the problem is a failed run capacitor that is attached electrically to the fan. When a run capacitor has gone bad its appearance may change, either looking swollen or leaking liquid. They are not very expensive, as most run capacitors for condenser fans are under 15 dollars, and can be obtained from your local air-conditioning supply store or repair shop. Remember to turn off the power before attempting any repair and write down where each wire is connected before disconnecting them. When going to the supply house either write down all the information that is printed on the capacitor, or take it with you to avoid any mistakes about the replacement part. It is safer to call the repair service, but it can also be more expensive.

The fan motor

If the run capacitor is not at fault, then the fan motor may need to be replaced. Printed on the side of the motor you will find the RPM (rotations per minute), the voltage requirements, the rotational direction, and the horsepower. A fan motor must have an exact match replacement, so if a new run capacitor is recommended, check the new motor for the correct rating. To obtain the exact replacement take down the model and serial numbers from the outside nameplate on the condenser and call around to the air-conditioning supply houses and repair shops in your town. Condenser fan motors can run anywhere from $100 to $200. Special tools are sometimes required to remove the fan blade from the motor, and special care should be taken not to bend the blades at all. A bent fan blade will not spin smoothly on the new motor and could cause major damage to the condenser coil if it is not attached to the new motor securely.

Be smart

Electricity, motor wiring and mechanical connections are a difficult undertaking. If you have doubts about doing it yourself, it would be better to call an experienced repairman. The intent of this article is to help you to make informed observations and decisions about your compressor fan situation.

About the Author

Susan King is a teacher with 27 years experience with all ages, grade levels and ability levels, including teaching in China. She has written a book, "The Road to Rebecca," about adopting from China. She graduated from Texas A&M University. She also has a ThM from Colorado Theological Seminary in Christian Counseling and recently received her PhD.

Photo Credits

  • photo by Jeff King